The invention relates to a bung keg of thermoplastic material having at least one carry and transport ring molded in one piece with the envelope. The envelope of the keg is arranged in the vicinity of an associated head surface, and has a vertical bearing surface for the jaws of a keg grab.
Plastic kegs equipped in this way can be picked up and transported, without any hand manipulation, using conventional keg grabs of a lift truck.
Ordinarily, such carry and transport rings have a cross section with a horizontal and a vertical web. The free end of the vertical web points towards the head surface of the keg, while the horizontal web is molded radially outward from the bottom of the barrel.
The rationale for this ring design, is so the jaws of the keg grab can slide under the annular web directed horizontally outward, and behind the web that is directed vertically upward. By using such a design, the whole load of the keg is transmitted to the lower jaw through the web directed horizontally outward, while the jaw engaged behind the vertical web secures the keg from slipping. This design permits the kegs to be hoisted and transported.
The kegs are normally constructed using a blow molding method. In this process, two mold halves, which are separable along a vertical plane, are used. The upper and lower region of each mold half is horizontally divided to provide mold parts which slide one into the other.
An extrusion head of the blowing machine delivers a parison or preform of extruded plastic between the mold halves which are in the separated position. During this extrusion process, the sliding mold parts in each mold half are opened. After the parison is lowered in the axial direction of the drum into the mold, the two mold halves are closed. In the closed position the mold halves clamp the previously extruded parison at what will be the head and bottom ends of the drum creating a seam across both clamped portions of the parison. The blowing process is then commenced. Molding apparatus of this type is conventional. A mandrel expands the parison so that it is pressed outwardly against the inner wall of the closed mold and, as a result, assumes the predetermined shape of the drum. With the upper and lower mold parts of each mold half disposed in an open position, the material of the parison enters into the recesses formed by the open mold parts. With such a mold construction, radially outwardly extending channels are formed on the container during the blow molding operation. These channels open toward the inside of the container.
Subsequently, the mold parts are moved relative to one another into a closed position. The mold parts which can be moved relative to one another are shaped to provide the carry and transport ring configuration and the material of the channels pressed into the recesses provided by the mold parts forms the carry and transport ring when the mold parts are moved relative to one another. It is in this ring area that the highest tensile and bending stresses are found.